1. Field of the Invention
The present invention relates to a liquid ejection head that ejects liquid such as ink, a recording apparatus having the same and a recording method, such as an ink jet recording head that performs recording with ejected ink droplets.
2. Description of the Related Art
In a liquid ejection head, for example, an ink jet recording head (hereinafter referred to as recording head) used in an ink jet recording apparatus, a recording element substrate provided with a plurality of heaters, such as heating resistance elements, is used as a liquid ejecting substrate for ejecting liquid (e.g., ink). The speed of recording increases with an increase in the number of recording elements provided in a recording element substrate, or with an increase in the recording width.
Japanese Patent Laid-Open No. 2007-160834 discloses a so-called full-line type recording head in which a plurality of recording element substrates are disposed, and that has the same width as a recording medium to achieve further high-speed recording.
As shown in FIGS. 12 and 13, the recording head, for example, of a full-line type, has a plurality of recording element substrates 1100a to 1100d disposed on a main surface of a single supporting plate 1200. Each recording element substrate is electrically connected with an electric wiring member 1300.
This supporting plate 1200 is joined to and held by an ink supplying member 1500 and constitutes an ink jet recording head 1000. In the ink supplying member 1500 is formed a liquid chamber for supplying ink to the recording element substrates.
Japanese Patent Laid-Open No. 2007-290245 describes a full-line type recording head in which a plurality of liquid chambers are formed in an ink supplying member 1500 to facilitate the removal of bubbles.
In general, members constituting a recording head may differ from each other in characteristics and function, and therefore also differ from each other in linear expansivity.
Specifically, recording element substrates 1100 each having an ejection port group for ejecting ink may be formed of silicon, which has a relatively low linear expansivity.
The recording element substrates 1100 are supported by, and fixed to, a supporting member. When the temperature changes, the difference in linear expansivity between the supporting member and the recording element substrates 1100 can cause warping. Reducing such warping can prevent the recording element substrates from being deformed or damaged. Therefore, the supporting member may be formed of a material that has a relatively high rigidity and a linear expansivity that is close to the linear expansivity of the recording element substrates 1100, such as for example a ceramic material.
An ink supplying member supplies liquid such as ink to the recording element substrates through the supporting member. The ink supplying member has a flow passage and a liquid chamber for supplying ink to the recording element substrates, and a shape adapted for fixing of the recording head to the recording apparatus. Therefore, the ink supplying member may be formed of resin by injection molding, which method may provide a relatively high degree of freedom of the member shape. The supporting member and the ink supplying member are joined, for example, with an adhesive.
In the case of the above recording head, the linear expansivity of the liquid supplying member formed of resin is relatively large compared to the linear expansivity of the recording element substrates and the supporting member formed of metal or ceramic.
In the case of serial-scan-type recording heads, which typically are not very long in size, if warping attributed to the difference in linear expansivity occurs when temperature changes, recording is generally not affected.
However, in the case of full-line type recording heads, the recording heads may be relatively long-sized in the longitudinal direction compared to serial scan type recording heads, and therefore warping attributed to the difference in linear expansivity among members may be significant. Therefore, problems caused by the warping can affect the recording.
The temperature change causing the above-described warping can occur in the recording head during either the assembly of the recording head, or during the use of the recording apparatus.
In general, when bonding members together that have significantly different linear expansivities, a flexible adhesive may be used to mitigate the effect of the warping. Most flexible adhesives are capable of bonding at room temperature, and therefore the temperature change during assembly may not be a problem.
However, when bonding members together that have significantly different linear expansivities and that are also relatively long-sized, the adhesive may not be able to absorb the warping caused by the temperature change of the recording head during the use of the recording apparatus, even when a flexible adhesive capable of bonding at room temperature is used. Therefore, the bonding strength may decrease, and peeling may occur.
When the recording head is assembled using an adhesive capable of bonding at high temperature, the temperature change of the recording head from the high temperature provided during the assembly process, back to room temperature, may create warping issues. An example of the warping attributed to a difference in linear expansivities between members that expand or contract due to temperature change, will be qualitatively described with reference to FIGS. 14A to 14C.
In FIG. 14A, the center in the longitudinal direction of the recording head is the origin, the direction of arrows represents the direction of displacement, and the length of arrows represents the magnitude of displacement. The longitudinal direction of the recording head is parallel to the longitudinal direction of the supporting member 1200. With the increasing distance from the center (origin) in the longitudinal direction of the recording head (in the longitudinal direction of the supporting member 1200), that is, with the decreasing distance from each end, the magnitude of displacement during expansion or contraction increases, and therefore the amount of the warping attributed to the difference in linear expansivity also increases. When the supporting member 1200 and the liquid supplying member 1500 are bonded at high temperature (FIG. 14A), the liquid supplying member 1500 contracts more significantly than the supporting member 1200 in the process of cooling to room temperature, and therefore warping may occur (FIG. 14B). The warping may cause the supporting member 1200 to peel off the liquid supplying member 1500 at each end (FIG. 14C).
If warping occurs and the supporting member 1200 is deformed as shown in FIG. 14B, the accuracy in placement of the recording element substrates is reduced, and thus the recording quality may be affected, even if the amount of deformation is small. In addition, the ink supplying member 1500 itself may be unacceptably deformed.
Also, if peeling occurs at each end as shown in FIG. 14C, it can significantly affect the recording operation.